1. Field of the Invention
The present invention relates to semiconductor memories. More particularly, the present invention relates to an adjustable sense amplifier circuit for read/write control of semiconductor memories.
2. Description of the Prior Art
Semiconductor devices are becoming increasingly sophisticated. One aspect of this sophistication is the need to integrate more and more circuitry onto smaller and smaller areas of silicon. Integrated circuit functions are comprised of linked circuit subfunctions. The subfunctions, in turn, are composed of individual circuit elements that are integrated onto a semiconductor substrate. The need to provide more and more functional groupings of components in less and less space makes the area available for circuitry on the semiconductor substrate more valuable. The elimination of unnecessary circuit elements from semiconductor integrated circuits creates space to add additional circuit subfunctions, and thereby increases the sophistication of the function performed by the integrated circuit. Additionally, the elimination of unnecessary circuit elements and their associated circuit pathways improves the speed and efficiency of the integrated circuit while lowering circuit power consumption and manufacturing cost.
A recent prior art read/write control circuit for a semiconductor memory is alluded to in a paper entitled "A Fast 7.5 ns Access 1K-Bit RAM for Cache-Memory Systems" which appeared at page 656 of the IEEE Journal of Solid-State Circuits, Vol. SC-13, No. 5, October, 1978. Additional prior art references are shown in an IEEE Press book entitled "Semiconductor Memories", at pages 37 and 45 Edited by David A. Hodges, and another book entitled "Semiconductor Memory Design and Application" at pages 97 et seq. by G. Luecke, et al., 1973, published by the McGraw-Hill Book Company.
A write and read control circuit for semiconductor memories is described in U.S. Pat. No. 4,272,811 issued to Wong on June 9, 1981, and assigned to the assignee of the present invention. The Wong patent discloses a circuit for controlling write and read functions in a semiconductor memory having a plurality of memory cells and of the type wherein the memory cell state is determined by a sense amplifier. Sense level in the Wong circuit depends on a plurality of diode and resistor voltage divider circuits.